const CDN_HOST = 'img.yidaima.cn'

// JPEG is used deliberately here. Some older iOS/WeChat image decoders cannot
// display the WebP thumbnails returned by Qiniu.
const ARTICLE_CARD = 'imageView2/1/w/600/h/375/format/jpg/q/75/ignore-error/1'
const RESOURCE_CARD = 'imageView2/1/w/500/h/400/format/jpg/q/75/ignore-error/1'

function original(url) {
  if (!url || typeof url !== 'string') {
    return url || ''
  }

  const value = url.trim()
  const httpPrefix = `http://${CDN_HOST}/`
  if (value.indexOf(httpPrefix) === 0) {
    return `https://${value.substring('http://'.length)}`
  }
  if (value.indexOf(`//${CDN_HOST}/`) === 0) {
    return `https:${value}`
  }
  return value
}

function qiniuThumbnail(url, operation) {
  const normalized = original(url)
  if (!normalized || normalized.indexOf(`https://${CDN_HOST}/`) !== 0) {
    return normalized
  }
  // Keep signed or already processed URLs intact.
  if (normalized.indexOf('?') >= 0) {
    return normalized
  }
  return `${normalized}?${operation}`
}

function compatibleThumbnail(url) {
  const normalized = original(url)
  if (!normalized) {
    return ''
  }

  // The API may still return a cached showImgThumb containing format/webp.
  // Rewrite that Qiniu operation on the client while the backend rolls over.
  if (normalized.indexOf(`https://${CDN_HOST}/`) === 0) {
    return normalized.replace(/\/format\/webp(?=\/|$)/i, '/format/jpg')
  }
  return normalized
}

function articleThumbnail(image) {
  if (image && typeof image === 'object') {
    return compatibleThumbnail(image.showImgThumb) || qiniuThumbnail(image.showImg, ARTICLE_CARD)
  }
  return qiniuThumbnail(image, ARTICLE_CARD)
}

function resourceThumbnail(image) {
  if (image && typeof image === 'object') {
    return compatibleThumbnail(image.showImgThumb) || qiniuThumbnail(image.showImg, RESOURCE_CARD)
  }
  return qiniuThumbnail(image, RESOURCE_CARD)
}

export default {
  original,
  compatibleThumbnail,
  articleThumbnail,
  resourceThumbnail
}